The use of coated textile composites or laminates of textiles and liquid protective barrier membrane layers to create liquidproof protective apparel and protective footwear is well known in the industry. The most common of these applications is waterproof breathable apparel. Typical examples are laminate materials sold by W. L. Gore and Associates, Inc. under the registered trade name GORE-TEX, which contain a waterproof breathable film laminated, or bonded, to one or more textile layers. These laminates are fabricated into apparel and footwear and sold as GORE-TEX® garments and the like. Coated textiles can also be used in textile composites for these same purposes. Both coated textiles and protective barrier membrane, or film, laminates will be collectively referred to hereafter as “laminates” solely for convenience of description.
Pieces or panels of these laminates are joined together to form garments and other similar textile structures. In the case of footwear, pieces or panels of laminates are typically joined together to form booties which are then integrated as a liner in the shell of the footwear and combined with the sole. For the garments and footwear to be liquidproof and protective, there is a need to seal the seams where the panels of laminate are joined together. The joining of these laminate panels is typically done by first sewing the laminates together using conventional sewing techniques. Liquidproof sealing of these sewn seams is then accomplished by the application of a seam seal tape having a thermoplastic hot melt adhesive which seals to the surface of the coating or protective barrier film and creates a seal over the sewing holes and the area where the layers join between the stitches. The seam seal tape may be heated, for example, using a nozzle to direct a stream of hot air so as to melt the adhesive. The tape is then applied over the seam and both are passed through the nip of a pair of pressure rollers in order to squeeze the molten adhesive onto the protective layer surface to ensure good bonding of the tape to the surface. For aesthetic reasons, the seam sealing tape is generally applied to the interior of a garment so that it is hidden from view. In the case of a bootie for covering the foot, the seam sealing tape is generally applied to the exterior of a bootie which is between the lining material and the shell of the footwear so that it is hidden from view. Less common sealing techniques such as gluing and welding are also known in the art.
In many applications, it is desirable to use a textile layer on both sides of the protective membrane or coating, either to extend the durability of the protective layer, or to improve the aesthetics and sensorial comfort of the finished apparel and footwear. In the case of footwear, when a bootie is used as a liner, textile on both sides of the membrane improves the durability. In an alternative construction, such as is described in U.S. Patent Application Publication No. 2004/0139629 A1, a bootie made from a laminate with textile on both sides of the membrane can act as the shell, or upper, of the footwear as well as the liner. These laminates are referred to as three-layer constructions, or three-layer laminates. For example, very often for reasons of comfort and appearance the liquidproof, breathable laminate is provided with a knitted liner layer (i.e., the layer which faces the wearer), which is somewhat soft to touch and thus, provides improved comfort in contact with the wearer. In the special cases where these three-layer constructions comprise the upper of the footwear, the textiles need to have sufficient thickness and durability to maintain waterproofness and aesthetics for the footwear for the duration of its life expectancy.
Unfortunately, the liner layers which can be used with conventional liquidproof garments and footwear are very limited, as problems with creating a durable, liquidproof seal arise when layers with a complex textile structure are used. As used herein, the term “complex textile structure” is intended to refer to textiles with a fiber, or filament, structure (whether mono-filament or multi-filament) having a tortuous path through which adhesives or sealants have limited ability to penetrate to the protective barrier layer and to encapsulate the filaments of the textile layer in order to form a liquidproof seam. For the purposes of this invention, fibers and filaments are considered to be used interchangeably and can include, for example, staple fibers. Complex textile structures can include, for example, wovens, nonwovens, knits, and brushed, fleeced or otherwise napped (i.e, any suitable raised surface) forms thereof. These complex textile structure materials often tend to be bulkier or thicker than conventional liner layers and are more desirable since they tend to be more comfortable to the wearer.
As noted above, the use of textile constructions with three layers, and possibly even more layers in some instances, creates added difficulty in forming a liquidproof seam. Not only does a seal need to reach the protective barrier layer surface, but also the structure of the textile itself needs to be sealed or encapsulated to prevent liquid from wicking or seeping along the textile fibers and exiting beyond the boundary of the liquidproof seam. Thus, the seam sealing of such three-layer fabrics, such as those having a complex textile structure for the inner lining layer, has posed significant problems in the prior art.
A first problem is that while the application of heat and pressure to the seam sealed tape is generally effective to force the molten adhesive through the liner layer into good contact with the underlying membrane layer (thereby filling the spaces between adjacent yarns in the liner material), the seam seal adhesive does not penetrate within the interstices of the yarns themselves. As is known, yarns are made up of multiple filaments etc., which have interstices between adjacent filaments. These interstices provide a path along which liquid can wick or weep from the seam to the inside of the garment. This is depicted in more detail with reference to FIGS. 1 and 2, described below. Thus, liquid water entering into the seam through a gap between the adjacent pieces of material or through holes in the rows of stitching, is able to wick laterally out of the seam through the interstices in the yarns of the liner material itself. Therefore, the seam is not completely liquidproof, particularly under severe weather or challenge conditions.
FIGS. 1 and 2 illustrate the problems with conventional seam sealing procedures. FIG. 1 shows a series of steps for forming a conventional seam with the application of seam sealing tape. It is to be understood that the formation of the seam can generally be carried out using conventional sewing machines.
In step 1), two adjacent pieces of material 1a, 1b are overlapped along a seam 2. In a second step 2), the seam is stitched with a row of stitching 3. In a third step 3), the seam is folded over and a further line of stitching 4 is applied so as to form a flattened seam. This seam is not liquidproof, since liquid can ingress through the space between the overlapped pieces of material 1a, 1b. Liquid can also ingress through the holes formed by the stitching 3, 4. For this reason, it is conventional to apply a hot-melt seam sealing tape across the seam such that it seals to the material on either transverse side of the seam. This is shown in step 4), wherein a seam seal tape 5 has been applied across the seam. Seam seal tape is conventionally applied by applying a heated air stream to melt the hot melt adhesive applied to one side of the seam seal tape and pressing the seam seal tape against the seam using pressure rollers, whereby the hot melt adhesive is pressed into the yarns of the fabric such that the seam seal tape becomes securely adhered to the underlying fabric.
As mentioned previously, a problem with this conventional procedure is that the seam seal adhesive, while filling the spaces between adjacent yarns, does not penetrate into the interstices between filaments, etc., within the yarn itself. These interstices provide a route for liquid to wick through the seam in the direction of the arrows A. Thus, liquid enters the seams either between the adjacent pieces of material or through the stitching holes. It is then able to wick out in the direction of the arrows A, particularly under severe weather conditions or liquid challenges.
The problem is illustrated further in FIG. 2, which is a cross-section along line B-B′ across the area where the seam seal tape 5 is adhered to material 1b on one side of the seam area. The material 1b includes a liner material laminated thereto composed of individual yarns 6, each yarn is made up of a number of individual filaments, etc. The hot melt adhesive 7 on one side of the seam sealing tape 5 can be seen to have penetrated into the spaces between the yarns 6 but has not penetrated into the interstices between the individual filaments, etc., of the yarns. The pathways for potential liquid ingress A are shown again.
A second problem with the conventional seam sealing process is that the choice of liner layer fabrics which may be seam sealed is currently very limited. One reason for this is that complex textile liner layers require a great deal of heat and pressure to drive the adhesive into the spaces between the liner yarns and to form a strong bond with the underlying protective layer, which is not only time consuming to obtain a reliable seal, but costly as well. In addition, if too much pressure is applied between the seam seal rollers, the pattern of the liner material itself may impress through to the front face of the fabric (i.e., material 1a and 1b) and appear as an undesirable aesthetic. Even at such high pressures, formation of a reliable seam cannot be guaranteed.
In order to overcome these problems, the textiles used for the liner layer, or sealing side, of the laminate have been limited to somewhat open structures, such as relatively simple knits, to allow easy penetration of sealing adhesive. Mono-filament or low-filament count (e.g., 12-13 filament count or less) knits, which have a relatively open structure, are the easiest structures to durably seal for liquidproof apparel and are conventionally used to avoid the challenges of sealing the interstices of more complex multi-filament textiles.
In order to overcome the sealing limitations of textile structures identified above, a great deal of innovation has been directed to developing lower viscosity adhesives that can penetrate and seal complex textile structures. In U.S. Pat. No. 6,387,994, Gore et al. describe the use of solid solvent as a method to lower adhesive viscosity to allow adhesives to penetrate and seal somewhat more complex structures such as brushed knits. In PCT Publication No. WO 01/26495 A1, Dunham et al. describe the use of a liquid thermoset adhesive such as silicone in an effort to seal even more complex or thicker structures. All of these approaches, however, have limitations not only with respect to the thickness and complexity of textile structures that can be sealed, but also in the ease of manufacturing such garments.
In the footwear industry, skiving is a technique used to prepare the edges of two relatively thick and stiff leather pieces to be joined at seams. The skiving reduces the leather thickness for easier joining of the stiff components and helps to prevent thick, stiff seams that could rub and be uncomfortable to the wearer. These seams are typically not waterproof.
Skiving has also been used to improve the formability of leather in the lasting region, or margin, of the upper to reduce the thickness of leather being turned in a tight radius as would occur during the lasting process of footwear formation when joining the leather upper to the stiff insole board. In some instances in the production of waterproof footwear, a protective lining has been skived in addition to the leather to reduce wrinkling along the lasting margin and to allow attachment of the lining to a waterproof insole board in a liquidproof manner. However, such constructions are limited to the attachment of the liner and upper to the insole board or sole, and not used in the creation of waterproof seams between two joined laminate panels.
To date, commercially available liquidproof, breathable three-layer laminates and garments have been restricted to brushed knit liner layers of limited complexity and limited thickness to permit adequate liquidproof sealing of the seams; alternatively, garments and footwear having fleece liner layers have been sold, but they are not liquidproof at the seam, as it is not possible to seal through the complex textile structures on the inside or outside of the article.
Apparel incorporating selectively permeable films or impermeable films that are used as chemical barriers for chemical protection or even protection against chemical and biological warfare agents are also subject to the same limitations as liquidproof breathable apparel and footwear with liquidproof seams. In these applications it would be especially desirous to use three-layer (or more) laminate structures with complex textile structures to provide additional protection to the barrier layer, such as from puncture or abrasion during use. To date, no such protective apparel or footwear with these features exists.
Accordingly, a need exists in the footwear industry for a reliable and effective technique for joining two or more panels of a complex textile laminate construction to form a flexible liquidproof seam in protective footwear.
Definitions
“Laminate” is a protective film or coating that is coated onto or adhered to at least one layer of textile.
“Protective layer”, “barrier layer”, “functional layer”, or “film” are defined as a film or coating that provides a barrier to liquid water penetration as a minimum, and ideally to a range of liquid chemical challenges. The layer is considered liquidproof if it prevents liquid water penetration against a pressure of at least 0.07 bar for a duration of at least 3 minutes. The protective layer material preferably guarantees a water penetration pressure of more than 0.07 bar. The water penetration pressure is measured on a liquidproof panel based on the same conditions described with respect to the Suter Test for Liquidproof Seams, described herein.
“Seam” is defined as the area where 2 or more pieces of laminate are permanently joined together by sewing, gluing or other mechanical joining.
“Liquidproof seam” is a seam that will not leak or weep liquid when challenged with a test fluid at a pressure of at least 0.07 bar for a duration of at least 3 minutes. The test fluid is at minimum water, and ideally can be a range of liquid chemicals.
“Durably liquidproof seam” is defined as a seam that will not leak or weep fluid when challenged with a test fluid at a pressure of at least 0.07 bar for a duration of 3 minutes after 5 machine wash and dry cycles based on the Test for Durably Liquidproof Seams, described herein. The test fluid is at a minimum water, and ideally can be a range of liquid chemicals.
“Skiving” is defined as the removal of material or textile by cutting, grinding, sanding, abrading or the like from the laminate in the portion of the laminate where a sealed seam will eventually be formed, between two or more protective laminate panels.
“Footwear” is defined as a covering for the foot, such as a shoe, boot, sock or the like, which incorporates one or more laminate panels including a protective layer, said laminate panels being joined together by at least one durably liquidproof seam. The laminate panels may form a bootie as a liner within the footwear, or alternatively the joined laminate panels may comprise both liner and upper of the footwear when attached to or with other components of the footwear.